Electrophoresis is a process used for the separation and characterisation of materials, such as DNA, RNA and proteins using the property that charged particles migrate in the presence of an electric field. Electrophoresis is widely used in a variety of fields including forensic science, molecular biology, genetics, microbiology and biochemistry.
Frequently, electrophoresis involves the separation of molecules within a gel matrix which is typically agarose, polyacrylamide or starch. The gel matrix acts to resolve the molecules based upon size as differently sized molecules move through the gel matrix at different rates. The gel matrix also acts to maintain the finished separation such that it can be analysed at a later point in time.
Single cell gel electrophoresis, sometimes known as the “comet assay”, is a process by which DNA damage may be quantified in individual cells. The process may be run in neutral conditions where strand breaks in the DNA may be identified, and under alkaline conditions where alkali-labile sites or certain nucleobase modifications may also be identified. The principle of single cell gel electrophoresis is that strand breaks lead to a relaxation and unwinding of DNA under alkaline conditions. By subsequently applying an electric field, the DNA undergoes electrophoresis, that is, moving under the influence of the electric field which forms a ‘comet shape’ when viewed under a microscope. The amount of DNA in the comet ‘tail’ relative to the amount remaining in the comet ‘head’, is proportional to the number of strand breaks present. This provides a quantified measure of the DNA damage present in the cell of interest.
Single cell gel electrophoresis is conducted in a number of stages. In a typical procedure, the cell of interest is first embedded in low-melting agarose and then loaded onto a microscope slide which has been pre-coated with an agarose gel matrix. The gel is then subjected to a number of pre-electrophoresis steps including treatment at a high pH to lyse the cells and treatment with DNA repair enzymes. The slides are then transferred individually into an electrophoresis tank and electrophoresed. Following this, a number of post-electrophoresis steps are performed which may include neutralisation, washing, staining and drying. Finally, the cells are subjected to an imaging or scoring stage for analysis.
The multiple pre-electrophoresis and post-electrophoresis steps require the manipulation of multiple slides. In currently employed methods, the slides are manipulated individually through these steps, making the process laborious and time-consuming. Moreover, individual manipulation of slides presents an increased risk that the gels may become damaged, contaminated or lost.
Furthermore, the comet assay is conventionally performed with the microscope slides lying flat in the electrophoresis tank. A significant limitation to this convention is that placing microscope slides flat within the electrophoresis tank reduces the number of slides that can be contained within the tank at any one time, thus limiting the number of samples which can be electrophoresed in parallel.
It would therefore be advantageous to provide a method and/or apparatus for performing electrophoresis whereby each slide is not subjected to individual manipulation in a majority of steps of the process.
It would also be advantageous to provide a method and/or apparatus for performing electrophoresis which increases the throughput of the process.
It is an aim of embodiments of the invention to overcome or mitigate at least one of the problems of the prior art described above.